Servicing a nuclear reactor module

ABSTRACT

A system for servicing a nuclear reactor module comprises a crane operable to attach to the nuclear reactor module, wherein the crane includes provisions for routing signals from one or more sensors of the nuclear reactor module to one or more sensor receivers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/609,997 filed on May 31, 2017, which is a divisional of U.S. patentapplication Ser. No. 14/350,689 filed on Apr. 9, 2014, issued as U.S.Pat. No. 9,697,917 on Jul. 4, 2017, which is a national stageapplication of International Application No. PCT/US2012/027525 filedMar. 2, 2012, each of which is incorporated herein by reference in itsentirety.

BACKGROUND

In a nuclear reactor, a core of nuclear material is confined to a smallvolume internal to the reactor so that a reaction may occur. In manyinstances, a controlled nuclear reaction may persist for an extendedperiod of time, such as several years or even longer, before refuelingof the nuclear core is required. Accordingly, when used as a source ofheat for converting quantities of water into steam, a properly designednuclear reactor may provide a long-lasting, carbon-free, and highlyreliable source of energy.

Relatively small, modular or standalone nuclear reactors may be built ina manufacturing environment and transported to a reactor bay at a powergenerating facility that is far removed from the manufacturing location.A group of modular nuclear reactors of the same design may be aggregatedat the power generating facility to provide a multiple of the poweroutput of a single, standalone reactor module. This allows additionalmodules to be placed into service over time so that the output of apower generating station may be incrementally increased to keep pacewith a growing demand for electrical power. For example, a powergenerating station that initially employs two nuclear reactor modulesservicing a small town may incorporate additional modules in severalincrements as the town increases in size and the demand for electricalpower increases correspondingly.

When refueling a nuclear reactor module, a servicing crew maydisassemble various reactor components so that spent fuel can be removedand stored in a spent fuel pool. In addition to loading fresh fuel intothe reactor, the servicing crew may be required to perform additionalmaintenance operations. These operations may include inspecting thereactor module components for excessive wear, leak testing of componentsthat operate under pressure, and inspecting structural and load-bearingcomponents for stress cracks. In some instances, it may be useful toperform such servicing at a location separate from the reactor's normaloperating bay.

SUMMARY

In a general embodiment, a method of servicing a nuclear reactor moduleincludes decoupling one or more sensors of the nuclear reactor modulefrom a first sensor receiver, followed by coupling the one or moresensors of the nuclear reactor module to a second sensor receiver, andmoving the nuclear reactor module from a first location, such as areactor bay, to a second location, such as a servicing area.

A first aspect combinable with the general embodiment includesdisplaying a representation of at least one signal from the one or moresensors of the nuclear reactor module on a display located within aservicing area.

In a second aspect combinable with any of the previous aspects, therepresentation of the at least one signal from the one or more sensorsof the nuclear reactor module may be displayed on a display located in areactor operator area.

Include transmitting signals from the one or more sensors of the nuclearreactor module through a conduit located on a crane coupled to thenuclear reactor module to the second receiver.

In an aspect, which may be combinable with any previous aspect, thedecoupling and coupling occur in a sensor-by-sensor manner wherein afirst sensor of two or more sensors of the nuclear reactor module isdecoupled from the first sensor receiver and coupled to the secondsensor receiver prior to a second sensor of the two or more sensors ofthe nuclear reactor module being decoupled from the first sensorreceiver.

In an aspect of an embodiment, the method may further include comparinga signal level from the first sensor received by the first sensorreceiver with a signal level from the first sensor received by thesecond sensor receiver. Wherein, in an aspect that may be combinablewith any previous aspect, if the signal level from the first sensorreceived by the first sensor receiver approximates the signal level fromthe first sensor received by the second sensor receiver, the method mayinclude decoupling a second sensor from the first sensor receiver. In anaspect, which may be combinable with any previous aspect, the method mayfurther include approximately continuously monitoring the nuclearreactor module during the moving using the second sensor receiver.

In another embodiment, a system for servicing a nuclear reactor moduleincludes a crane operable to couple to the nuclear reactor module,wherein the crane includes a conduit for routing signals from one ormore sensors of the nuclear reactor module to one or more sensorreceivers. In an aspect, which may be combinable with any previousaspect, the crane may include a drive mechanism operable to move thenuclear reactor module from a reactor bay to a servicing area. In anaspect, which may be combinable with any previous aspect, the drivemechanism may move the nuclear reactor module in a first direction and asecond direction approximately orthogonal to the first direction. In anaspect, which may be combinable with any previous aspect, the crane mayfurther include at least one support bracket for mounting one or moresensor signal receivers operable to receive signals from one or moresensors within the nuclear reactor module. In an aspect, which may becombinable with any previous aspect, the system may further include adisplay operable to display representations of signals from the one ormore sensors of the nuclear reactor module in a servicing area and mayfurther include a display operable to display representations of signalsfrom the one or more sensors of the nuclear reactor module in anoperator area.

In another general embodiment, an apparatus includes a fastener operableto couple to a nuclear reactor module, an interface panel for acceptingone or more signals from the nuclear reactor module, and a deviceoperable to move the nuclear reactor module in a lateral direction.

In a first aspect combinable with the general embodiment, the device isoperable to move the nuclear reactor module in the lateral directionoperates to move the nuclear reactor module in a first direction and asecond direction approximately orthogonal to the first direction.

A second aspect combinable with any of the previous aspects includes atrack for maintaining a minimum bend radius of at least one conductorconveying the one or more signal.

A third aspect, which may be combinable with any of the previousaspects, includes a controller for assisting and relocating a nuclearreactor module to a lower containment vessel removal fixture located ina servicing area. A fourth aspect, which may be combinable with any ofthe previous aspects, includes a conduit operable to hold a receiverthat receives signals from one or more sensors located within thenuclear reactor module.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative examples of the present invention aredescribed in detail below with reference to the following drawings:

FIG. 1 shows a crane fastened to a nuclear reactor module according toan example implementation.

FIG. 2 is a top view showing 12 nuclear reactor modules that may bemoved within a power generating station using an overhead craneaccording to an example implementation.

FIG. 3 is a diagram of a nuclear reactor module coupled to sensorreceivers and displays according to an example implementation.

FIG. 4 is a flowchart for a method for servicing a nuclear reactormodule according to an example implementation.

DETAILED DESCRIPTION

Methods, apparatuses, and systems for servicing a nuclear reactor moduleare described. In one implementation, pressure, temperature, sourcerange neutron count, and other operating parameters of the nuclearreactor module may be monitored while the module is in operation. Inpreparation for a refueling or other servicing operation, a first sensorreceiver located outside of the nuclear reactor module may be decoupledfrom sensors located within the reactor module. The sensors within thenuclear reactor module may then be coupled to a second sensor receiverby way of an electrical, fiber-optic, or other type of bundle routedalong a routing path that is attached to, or included within, anoverhead crane. Upon coupling of the sensors within the nuclear reactormodule to the second sensor receiver, the overhead crane may beactivated to move the module from an operating bay to a servicing area.

In another implementation, decoupling and coupling of sensors within thenuclear reactor module may occur in a sensor-by-sensor manner in whichan output signal level from a first sensor located within a nuclearreactor module may be recorded prior to decoupling the first sensor froma first sensor receiver. The first sensor may then be coupled to asecond sensor receiver. The output signal level recorded by the firstsensor receiver may then be compared with the output signal levelrecorded by the second sensor receiver to determine if an errorcondition in the first or the second sensor receiver is present. Anerror condition may also result from a defect in wire or fiber opticcable bundle used to couple a sensor to a sensor receiver. In the eventthat an error condition is not present, the comparison process may berepeated for a second sensor located within a reactor module beginningwith recording an output signal level from the second sensor, decouplingthe second sensor from a first sensor receiver, and comparing the outputsignal level received by the first sensor receiver with the outputsignal level received by the second sensor receiver to determine if anerror condition is present.

In an implementation, an overhead crane may include an interface panelthat receives output signals from two or more sensors within the nuclearreactor module prior to movement of the module. In this implementation,an operator may decouple the two or more sensors, as a group, from afirst sensor receiver and couple the group of one or more sensors to asecond sensor receiver by way of the interface panel. This allows thegroup of two or more sensors to be decoupled nearly simultaneously froma first sensor receiver and quickly coupled to a second sensor receiver.

As used herein and as described in greater detail in subsequentsections, embodiments of the invention may include various nuclearreactor technologies. Thus, some implementations may include reactortechnologies that employ pressurized water, which may include boronand/or other chemicals or compounds in addition to water, liquid metalcooling, gas cooling, molten salt cooling, and/or other cooling methods.Implementations may also include nuclear reactors that employ uraniumoxides, uranium hydrides, uranium nitrides, uranium carbides, mixedoxides, and/or other types of radioactive fuel. It should be noted thatembodiments are not limited to any particular type of reactor coolingmechanism, nor to any particular type of fuel employed to produce heatwithin or associated with a nuclear reaction.

FIG. 1 shows a crane (110) fastened to a nuclear reactor moduleaccording to an implementation. In FIG. 1, reactor core 20 is positionedat a bottom portion of a cylinder-shaped or capsule-shaped reactorvessel 70. Reactor core 20 comprises a quantity of fissile material thatproduces a controlled reaction that may occur over a period of perhapsseveral years or longer. Although not shown explicitly in FIG. 1,control rods may be employed to control the rate of fission withinreactor core 20. Control rods may comprise silver, indium, cadmium,boron, cobalt, hafnium, dysprosium, gadolinium, samarium, erbium, andeuropium, or their alloys and compounds. However, these are merely a fewof many possible control rod materials.

In implementations, a cylinder-shaped or capsule-shaped containmentvessel 10 surrounds reactor vessel 70 and is partially or completelysubmerged in a reactor pool, such as below waterline 90, within reactorbay 5. The volume between reactor vessel 70 and containment vessel 10may be partially or completely evacuated to reduce heat transfer fromreactor vessel 70 to the reactor pool. However, in other embodiments,the volume between reactor vessel 70 and containment vessel 10 may be atleast partially filled with a gas and/or a liquid that increases heattransfer between the reactor and containment vessels. Containment vessel10 rests on skirt 100 at the base of reactor bay 5.

In a particular implementation, reactor core 20 is submerged within aliquid, such as water, which may include boron or other additive, whichrises into channel 30 after making contact with a surface of the reactorcore. In FIG. 1, the upward motion of heated coolant is represented byarrows 40 within channel 30. The coolant travels over the top of heatexchangers 50 and 60 and is drawn downward by way of convection alongthe inner walls of reactor vessel 70 thus allowing the coolant to impartheat to heat exchangers 50 and 60. After reaching a bottom portion ofthe reactor vessel, contact with reactor core 20 results in heating thecoolant, which again rises through channel 30.

Although heat exchangers 50 and 60 are shown as two distinct elements inFIG. 1, heat exchangers 50 and 60 may represent any number of helicalcoils that wrap around at least a portion of channel 30. In anotherimplementation, a different number of helical coils may wrap aroundchannel 30 in an opposite direction, in which, for example, a firsthelical coil wraps helically in a counterclockwise direction, while asecond helical coil wraps helically in a clockwise direction. However,nothing prevents the use of differently-configured and/ordifferently-oriented heat exchangers and embodiments are not limited inthis regard. Further, although water line 80 is shown as beingpositioned just above upper portions of heat exchangers 50 and 60, inother implementations, reactor vessel 70 may include lesser or greateramounts of water.

In FIG. 1, normal operation of the nuclear reactor module proceeds in amanner wherein heated coolant rises through channel 30 and makes contactwith heat exchangers 50 and 60. After contacting heat exchangers 50 and60, the coolant sinks towards the bottom of reactor vessel 70 in amanner that induces a thermal siphoning process. In the example of FIG.1, coolant within reactor vessel 70 remains at a pressure aboveatmospheric pressure, thus allowing the coolant to maintain a hightemperature without vaporizing (i.e. boiling).

As coolant within heat exchangers 50 and 60 increases in temperature,the coolant may begin to boil. As the coolant within heat exchangers 50and 60 boils, vaporized coolant, such as steam moving upward asindicated by arrows 51 and 61, may be used to drive one or more turbinesthat convert the thermal potential energy of steam into electricalenergy. After condensing, coolant is returned to locations near the baseof heat exchangers 50 and 60 as shown by arrows 52 and 62.

During normal operation of the reactor module of FIG. 1, variousperformance parameters of the reactor may be monitored by way of sensorspositioned at various locations within the module. In the example ofFIG. 1, sensors within the reactor module may measure reactor systemtemperatures, reactor system pressures, containment vessel pressure,reactor primary and/or secondary coolant levels, reactor core neutronflux, and/or reactor core neutron fluence. Signals that represent thesemeasurements may be reported external to the reactor module by way ofbundle 120 to reactor bay interface panel 130. In one implementation,bundle 120 represents a multi-conductor cable. In anotherimplementation, bundle 120 may represent a single- or multi-fiberoptical transmission medium.

In the implementation of FIG. 1, crane 110 is shown as being positionedabove reactor bay 5. Crane 110 includes a cable or other device thatfastens to attachment 105, which may include a lifting lug, eyelet, orother device that couples an upper portion of containment vessel 10 tocrane 110. Thus, crane 110 operates to lift and suspend the nuclearreactor module of FIG. 1 in reactor bay 5. In implementations, crane 110includes a motor or other drive mechanism that enables the crane to movelaterally so as to allow the nuclear reactor module to be repositioned.

Prior to the upward or lateral movement of the nuclear reactor module ofFIG. 1, a connector at an end of bundle 120 may be detached from reactorbay interface panel 130, thereby decoupling one or more sensorsoperating within the reactor module from a first sensor receiver. In animplementation, bundle 120 may be attached to crane interface panel 135,thereby coupling the one or more sensors operating within the reactormodule to a second sensor receiver by way of crane interface panel 135.In FIG. 1, crane 110 includes provisions for routing bundle 140 through,for example, conduit 137, along an outside surface of at least a portionof the crane, or within the structure of crane 110 for connection toreceptacle 115. In an implementation, crane 110 includes a track formaintaining a minimum bend radius of bundle 140 while crane 110 movesfrom side to side. However, in other implementations, crane 110 mayinclude a rack for festooning or hanging portions of bundle 140 from asurface.

In an implementation, crane interface panel 135 may include, forexample, at least one set of brackets or a conduit that holds one ormore signal conditioning units or other sensor receivers that functionto convert electrical and/or optical signals from sensors located withinthe reactor module of FIG. 1. In one possible example, bundle 120 maycarry low-voltage signals from a thermocouple located within reactorvessel 70. Accordingly, crane interface panel 135 may include one ormore of an amplifier, an analog to digital converter, and a multiplexerthat converts and electrical signal conveyed on a conductor to anoptical signal transmitted along a single-fiber or multi-fiber opticaltransmission medium represented by bundle 140.

FIG. 2 is a top view showing 12 nuclear reactor modules that may bemoved within a power generating station using an overhead craneaccording to an implementation. In FIG. 2, containment vessel 10 of anuclear reactor module is shown within reactor bay 5. Crane 110 moves inboth an X and Y direction along track 150, wherein X and Y representorthogonal directions in a Cartesian coordinate system. In this manner,crane 110 may include a control capable of relocating or assisting inrelocating a nuclear reactor module from reactor bay 5, along track 150,to servicing area 160 where the nuclear reactor module may be placed onor proximate with a lower containment vessel removal fixture. Prior tomovement of a nuclear reactor module, sensors located within a reactormodule may be decoupled from a first sensor receiver to a second sensorreceiver by way of detaching a connector from a reactor bay interfacepanel to a crane interface panel, such as crane interface panel 135 ofFIG. 1.

FIG. 3 is a diagram of a nuclear reactor module coupled to sensorreceivers and displays according to an implementation. In FIG. 3,sensors from nuclear reactor module 200 have been decoupled from sensorreceiver 220 and operator display 230. In an implementation, operatordisplay 230 represents one or more displays located in a reactoroperator area. After such decoupling, sensors located within nuclearreactor module 200 are coupled to a second sensor receiver (240) by wayof interface panel 235 of crane 210.

After nuclear reactor module 200 has been coupled to sensor receiver240, module 200 may then be relocated from, for example, a reactoroperating bay to a servicing area. While module 200 is in transit fromthe reactor bay to the servicing area, sensors monitoring variousparameters may continue to provide output signals representing theconditions within the module. Representations of these parameters may bedisplayed on servicing area display 240, thus providing real-timemonitoring of conditions within reactor module 200 to a servicing crew.Additionally, representations of output signals reflecting theconditions within reactor module 200 may be displayed on operatordisplay 230 These representations on operator display 230 may beaccompanied by an identifier indicating that the module is “in transit”between and operating bay to a servicing area.

FIG. 4 is a flowchart for a method for servicing a nuclear reactormodule according to an implementation. The device of FIG. 3 may besuitable for performing the method of FIG. 4, although nothing preventsperforming the method of FIG. 4 using alternate arrangements ofcomponents in other embodiments. Implementations may include blocks inaddition to those shown and/or described in FIG. 4, fewer blocks, blocksoccurring in an order different from FIG. 4, or any combination thereof.In the method described in FIG. 4, sensors are coupled from a firstreceiver to a second receiver in a sensor-by-sensor manner as describedbelow. In an implementation, at least a portion of the method of FIG. 4may be performed by a controller or other hardware or software basedprocessing resource.

FIG. 4 begins at block 300, which includes recording a signal level froma first sensor of a nuclear reactor module received by a first sensorreceiver. At 310, the first sensor may be decoupled from the firstsensor receiver. At 320, the first sensor may be coupled to a secondsensor receiver. At 330, a signal level from the first sensor asreceived by the first sensor receiver is compared with the signal levelfrom the first sensor has received by the second sensor.

At 340, signal levels as received by first and second sensor receivermodules are compared. In the event that the comparison of block 340indicates that the signal levels are within a limit, block 350 isperformed in which a signal output from the next sensor received by afirst sensor receiver module may be recorded. In the event that thecomparison of block 340 indicates that the signal levels are outside ofa limit, block 360 may be performed in which a troubleshooting routinemay be performed.

While several examples have been illustrated and described, it will beunderstood by those skilled in the art that various other modificationsmay be made, and equivalents may be substituted, without departing fromthe scope of the following claims.

I/We claim:
 1. A device for moving a nuclear reactor, comprising: acoupling shaped to releasably engage the nuclear reactor; a drivemechanism positioned to move the nuclear reactor when the coupling isengaged with the nuclear reactor; and a signal receiver couplable to asensor positioned within a reactor vessel of the nuclear reactor,wherein the signal receiver is configured to receive signals from thesensor to monitor one or more parameters of the nuclear reactor as thedrive mechanism moves the nuclear reactor.
 2. The device of claim 1,further comprising an interface panel, wherein the interface panel isreleasably couplable to a cable of the nuclear reactor for receiving thesignals from the sensor positioned within the reactor vessel of thenuclear reactor.
 3. The device of claim 1, further comprising: a frame,wherein the drive mechanism is positioned to move the frame to move thenuclear reactor when the coupling is engaged with the nuclear reactor;an interface panel coupled to the frame, wherein the interface panel isreleasably couplable to a first cable of the nuclear reactor forreceiving the signals from the sensor positioned within the reactorvessel of the nuclear reactor; and a second cable coupled between theinterface panel and the signal receiver for routing the signals from theinterface panel to the signal receiver.
 4. The device of claim 3 whereinthe signal receiver is coupled to the frame such that the signalreceiver moves with the nuclear reactor when the drive mechanism movesthe nuclear reactor.
 5. The device of claim 3 wherein the signalreceiver is spaced apart from the frame such that the signal receiverdoes not move with the nuclear reactor when the drive mechanism movesthe nuclear reactor.
 6. The device of claim 3, further comprising atrack positioned to receive the second cable, wherein the track isshaped to maintain a minimum bend radius of the second cable when thedrive mechanism moves the nuclear reactor.
 7. The device of claim 1wherein the drive mechanism is positioned to move the nuclear reactorboth vertically and laterally.
 8. A system for moving a nuclear reactorand monitoring one or more parameters of the nuclear reactor, the systemcomprising: a crane positioned to releasably engage and move the nuclearreactor; and a signal receiver couplable to a sensor positioned within areactor vessel of the nuclear reactor, wherein the signal receiver isconfigured to receive signals from the sensor representative of the oneor more parameters of the nuclear reactor as the crane moves the nuclearreactor.
 9. The system of claim 8, further comprising a track, whereinthe crane is constrained to move along the track.
 10. The system ofclaim 9 wherein the crane is constrained to move along the track only ina first direction and a second direction orthogonal to the firstdirection.
 11. The system of claim 8, further comprising: a first drivemechanism positioned to move the crane in a first direction; and asecond drive mechanism positioned to move the nuclear reactor in asecond direction different than the first direction.
 12. The system ofclaim 11 wherein the first direction is a lateral direction relative toa reactor bay positioned to receive the nuclear reactor in a normaloperating state, and wherein the second direction is a verticaldirection relative to the reactor bay.
 13. The system of claim 8 whereinthe crane is positioned to move the nuclear reactor from a reactor bayto a servicing area, wherein the reactor bay is positioned to receivethe nuclear reactor in a normal operating state, and wherein theservicing area is positioned to receive the nuclear reactor in aservicing state.
 14. The system of claim 8 wherein the signal receiveris coupled to the crane such that the signal receiver moves togetherwith the crane.
 15. The system of claim 8, further comprising a displayoperably coupled to the signal receiver for displaying a representationof the one or more parameters.
 16. A nuclear reactor system, comprising:a nuclear reactor including a reactor vessel for receiving a reactorcore; a sensor positioned within a reactor vessel of the nuclearreactor; a reactor bay positioned to receive the nuclear reactor in anormal operating state; a servicing area positioned to receive thenuclear reactor in a servicing state; a moving device positioned to movethe nuclear reactor between the reactor bay and the servicing area; anda signal receiver configured to receive signals from the sensorrepresentative of one or more parameters of the nuclear reactor as themoving device moves the nuclear reactor.
 17. The nuclear reactor systemof claim 16 wherein the moving device is a crane positioned to (a) liftthe nuclear reactor vertically from the reactor bay and (b) move thenuclear reactor laterally from the reactor bay to the servicing area.18. The nuclear reactor system of claim 16 wherein the signal receiveris a first signal receiver, and further comprising: a first interfacepanel positioned on the moving device and coupled to the first signalreceiver; a second interface panel positioned proximate to the reactorbay and coupled to a second signal receiver; and a cable (a) fixedlycoupled to the sensor positioned with the reactor vessel and (b)interchangeably couplable to the first interface panel or the secondinterface panel.
 19. The nuclear reactor system of claim 16, furthercomprising a display operably coupled to the signal receiver fordisplaying a representation of the one or more parameters as the movingdevice moves the nuclear reactor.
 20. The nuclear reactor system ofclaim 19 wherein the display is a first display and further comprising asecond display, wherein the first display is positioned in the servicingarea, wherein the second display is positioned away from the servicingarea, and wherein the second display is operably coupled to the signalreceiver for displaying another representation of the one or moreparameters as the moving device moves the nuclear reactor.